The present invention relates to an internal combustion engine, and in particular is concerned with an improvement relating to the running under idling condition of an internal combustion engine in an automobile or other vehicle which is equipped with a heater and optionally with an air conditioner.
In order to minimize fuel consumption during idling, and also in order to minimze emissions of harmful exhaust gas components, the idling speed of an internal combustion engine is preferably set as low as possible consistent with stable rotation of the engine. That is, if the idling rotational speed is set too low, it will tend to fluctuate, and the engine will have a tendency to stall. If, on the other hand, the idling speed is set too high, fuel consumption and emissions of harmful exhaust gas components will be higher than necessary. Also problems will arise with the transmission, such that, if the vehicle is equipped with an automatic transmission, substantial "creep" will occur, making the vehicle difficult to control, and also leading to wear and premature failure of the transmission; whereas if the vehicle is equipped with a manual transmission, difficulty may well be experienced in getting the vehicle into gear from the neutral gearbox condition, and severe wear and possible premature failure of both the friction engaging means of the clutch system and of the synchromesh components of the gearbox may well occur.
When a vehicle is equipped with an air conditioner, the idling speed needs to be set somewhat higher when the air conditioner is operating than when it is not operating, since the conditioner imposes a substantial torque load on the engine. If the engine idling setting is not increased, the rotational speed of the engine will drop, and become unstable and liable to fluctuate, as described above, and the engine will tend to stall. When the engine idling setting is increased when the air conditioner is operating, more power is developed by the engine and is available for operating the air conditioner. Therefore, it has been the practice, in cars equipped with air conditioners, to incorporate an "idle-up" mechanism to increase the idling setting of the engine when the air conditioner is switched on.
On the other hand, in the case of a vehicle equipped with a heater which uses heat in the cooling water of the engine to heat the interior of the passenger compartment, the heater itself does not impose a torque load on the engine directly when it is functioning, since the heat is obtained from the cooling water of the engine, and the power required to blow air past the vanes of the heater is obtained either via an electric motor from the battery of the engine or from merely diverting a portion of the airstream which is in any event being propelled by the rotation of the engine fan.
However, a problem can occur when the heater of a car is operated while the vehicle is idling at the curbside. In these circumstances the heater often fails to work properly. The reason for this is that if the engine idle setting is as low as possible consistent with stable running, little heat will be generated in the engine and the temperature of the cooling water will fall, and, therefore, the heater will function at reduced efficiency.
In view of the aforementioned problem with regard to the operation of a heater in a vehicle, it has been envisaged in a co-pending U.S. patent application, Ser. No. 919,214, now abandoned, assigned to the same assignee as the present application, to provide, in a vehicle equipped with a heater, a mechanism which increases the idling setting of the engine when the heater is being operated, so as to consume more fuel and, therefore, to deliver more heat to the engine cooling water, thereby causing the heater to run warmer and more effectively.
Further, in the case of a vehicle which is equipped with both an air conditioner and a heater, it has in the aforementioned co-pending application been envisaged to use the same idling speed increasing mechanism to increase the idling speed either when the heater is being operated or when the air conditioner is being operated, since in both cases "idle-up" is desired, although for different reasons.
However, the increase of idling speed when the heater is operating, in an automobile equipped with the idling speed increasing mechanism above outlined, is rather greater than the increase of the idling speed when the air conditioner is operating, for the reason that the heater imposes no additional torque load on the engine, whereas the air conditioner, when operating, imposes a considerable torque load on the engine, and thus diminishes its idling rotational speed. When the heater is functioning, therefore, and the "idle-up" device is operating, an undesirably high increase in idling engine revolutions will occur, if the setting of the "idle-up" device is determined so as to provide the most desirable increase of idling speed when the air conditioner is being operated, and this in practice has been found to have disadvantages, such as outlined above, concerning "creep" in vehicles equipped with automatic transmissions, and concerning shifting the vehicle into gear from the gearbox neutral position, in vehicles equipped with manual transmissions and friction engaging means.
Therefore, in this case it appeared to be a desirable object to arrange some way of restraining this increase in engine idling speed, while still keeping the throttle of the automobile slightly opened in idling condition via the operation of the "idle-up" device, while the heater was functioning, in order to increase consumption of fuel and to supply more heat to the engine cooling water.